A computer system displays an annotation placement user interface that includes a representation of a field of view of one or more cameras that is updated over time based on changes in the field of view, and a placement user interface element indicating a location. If the placement user interface element is over a representation of a first type of feature in the physical environment, the appearance of the placement user interface element changes to indicate an anchor point corresponding to the first type of feature, and the system displays a first set of guides. If the placement user interface element is over a representation of a second, different type of feature in the physical environment, the appearance of the placement user interface element changes to indicate an anchor point corresponding to the second type of feature, and the system displays a second, different set of guides.